The invention relates to a radial blower for a work apparatus, especially for a suction/blower apparatus.
Radial blowers of the above kind draw air by suction through an end face intake opening, which is arranged in the region of the rotational axis of the blower wheel, and accelerate this air radially and tangentially outwardly via the blower wheel. The air is accelerated along an essentially spirally shaped running path because of the peripheral wall of the blower housing and is discharged from the blower housing via a peripheral discharge stub aligned approximately tangentially.
In practice, work apparatus with such radial blowers are operated under ambient conditions which are greatly laden with dirt, for example, for cutoff machines or chain saws having a radial cooling blower and especially for a suction/blower apparatus having a radial blower whose air flow intensely entrains dirt particles, dust grains, or sand grains, et cetera. The dirt particles likewise reach a considerable velocity during the acceleration operation and rub against the side and peripheral inner walls of the blower housing with a considerable level of energy. The entrained dirt particles have a considerably higher specific weight than air. For this reason, these dirt particles impinge with a velocity component, which is directed normally to the surface of the peripheral wall, against the inner side of the peripheral wall. This impact operation as well as the rubbing of the dirt particles against the inner walls can lead to a considerable wear of the blower housing.
Configuring the blower housing with thicker walls in the wear-endangered regions makes the component heavy and difficult to manipulate. A material selection, which corresponds to the requirements of the wear protection for the blower housing, compels a critical compromise between manipulability, weight and material strength.
It is an object of the invention to further improve a radial blower in such a manner that it has an increased resistance against wear with simple means and a cost-effective use of material.
The radial blower of the invention is for a work apparatus including a suction/blower apparatus and includes: a blower wheel defining a periphery; a blower housing at least partially enclosing the blower wheel; the blower housing having a peripheral wall and a side wall; the side wall having an intake opening; the blower housing further having a discharge stub arranged in the region of the peripheral wall opposite the periphery of the blower wheel; the peripheral wall and the side wall conjointly defining a wall surface facing toward the blower wheel; and, the wall surface being lined with a wear insert configured as one piece.
A functional separation of the blower housing from the surface, which is subjected to wear, is achieved with the arrangement of a separate wear insert in the blower housing. In this way, both components can be correspondingly optimized to the requirements especially with respect to the selection of materials therefor. In this way, the blower housing can therefore be configured to be thin-walled and therefore light, for example, from a stiff, strong and cold-flexible material and, in this way, the blower housing can serve as a carrier for a wear insert optimized as to wear strength. Abutting edges are avoided by making the wear insert as one piece. Otherwise, dirt can deposit between such abutting edges. It is also avoided that dirt particles become lodged between the wear insert and the blower housing which would otherwise lead to a lifting of the wear insert from the blower housing. By making the wear insert as one piece, there further results a configuration of the wear insert which leads to a form-tight fit with the blower housing and this contributes to a close bond of both components.
The dirt particles can be propelled far into the discharge stub because of their combined radial and tangential path. For this reason, the wear insert preferably extends into the discharge stub. The discharge edge is formed between the discharge stub and the peripheral wall close to the blower wheel. This discharge edge is purposefully configured so as to be rounded and is additionally protected by a strengthening of the wear insert in this region.
By configuring the blower housing from two half shells, the partition plane of the two half shells forms a partition line along which also a free edge of the wear insert runs. The two half shells are preferably so configured that the partition plane lies perpendicularly to the blower axis. In this way, the partition plane can be constructively so placed that the sensitive peripheral free edge of the wear insert lies outside of the peripheral region of the blower wheel and therefore outside of the direct impact caused by free flying dirt particles. In this way, other requirements can be considered also, such as easy assembly. Even if the partition line should lie in the peripheral region of the blower wheel, it is ensured that the free edge of the wear insert does not lie perpendicularly to the tangentially running fly path of the dirt particles. In this way, it is ensured that the dirt particles, which fly with high kinetic energy, cannot deposit between the wear insert and the blower housing.
A further free edge of the wear insert lies in the region of the side wall annularly about the intake opening. To protect this free edge, a shoulder is provided in the side wall and this shoulder rises in the axial direction. This shoulder forms an approximately circularly-shaped concave edge and an approximately circularly-shaped convex edge in the side wall. The wear insert extends in the radial direction from the peripheral wall and along the side wall around the convex edge and over the shoulder and into the concave edge. The free edge of the wear insert is well protected in the concave edge against direct impact of high-energy particles. The convex edge is preferably configured so as to be rounded whereby a reduced flow resistance can be achieved.
The permanence of form and the general ability of the blower housing to withstand load under various conditions is ensured by an embodiment in preferably injection-molded plastic and especially in glass-fiber reinforced polyamide. The wear insert is purposefully formed of an elastic plastic, rubber or a rubber mixture especially in the bond to a blower housing of this type of configuration whereby a high resistance to wear and high impact damping can be achieved.
A permanent bond of the wear insert to the blower housing can be achieved in that both parts form a surface melt bond with each other. In this way, an adherence strength between the two parts can be achieved which can even lie above the material strength of the wear insert. In this way, it is achieved that the resistance to wear is determined alone by the material characteristics of the wear insert without having to accept a premature failure by separation of the wear insert from the apparatus housing.